Old Style and New Style dates

This article is about the 18th-century changes in calendar conventions used by Great Britain and its colonies specifically. For a more general discussion of the equivalent transitions in other countries, see Adoption of the Gregorian calendar.

Issue 9198 of the London Gazette, covering the calendar change in Great Britain. The date heading reads: "From Tuesday September 1, O.S. to Saturday September 16, N.S. 1752."

Old Style (O.S.) and New Style (N.S.) are terms sometimes used with dates to indicate that the calendar convention used at the time described is different from that in use at the time the document was being written. There were two calendar changes, which may sometimes complicate matters: the first change was to change the start of the year from Lady Day (25 March) to 1 January; the second was to discard the Julian Calendar in favour of the Gregorian Calendar.[1][2][3] Closely related is the custom of dual dating, where writers gave two consecutive years because of differences in the starting date of the year, or included both the Julian and Gregorian dates.

Beginning in 1582, the Gregorian calendar replaced the Julian in Roman Catholic countries. This change was also implemented in Protestant and Orthodox countries, usually at much later dates. In England and Wales, Ireland, and the British colonies, the change of the start of the year and the changeover from the Julian calendar occurred in 1752 under the Calendar (New Style) Act 1750. In Scotland, the legal start of the year had already been moved to 1 January (in 1600), but Scotland otherwise continued to use the Julian calendar until 1752.[4]

Start of the year in the historical records of Britain and its colonies and possessions[edit]

A contemporary memorial plaque showing date of death as January 1708/9

When recording British history it is usual to use the dates recorded at the time of the event,[a] with the year adjusted to start on 1 January. But the start of the Julian year was not always 1 January, and was altered at different times in different countries.

From 1155 to 1752, the civil or legal year in England began on 25 March (Lady Day)[5][6]so for example the execution of Charles I was recorded at the time in Parliament as happening on 30 January 1648 (Old Style).[7] In modern English language texts this date is usually shown as "30 January 1649" (New Style).[1] The corresponding date in the Gregorian calendar is 9 February 1649, the date by which his contemporaries in some parts of continental Europe would have recorded his execution.

The O.S./N.S. designation is particularly relevant for dates which fall between the start of the "historical year" (1 January) and the official start date, where different. This was 25 March in England and Wales until 1752 (see Julian year).

During the years of transition between the first introduction of the Gregorian calendar in continental Europe and its introduction in Britain, contemporary usage in England started to change.[3] In Britain 1 January was celebrated as the New Year festival,[8] but the "year starting 25th March was called the Civil or Legal Year, although the phrase Old Style was more commonly used."[3] To reduce misunderstandings about the date, it was normal in parish registers to place a new year heading after 24 March (for example "1661") and another heading at the end of the following December, "1661/62", to indicate that in the following few weeks the year was 1661 Old Style but 1662 New Style.[9] Some more modern sources, often more academic ones, also use the "1661/62" style for the period between 1 January and 25 March for years before the introduction of the Gregorian calendar in England. (See for example The History of Parliament).[10]

In contrast, the United States typically translates notable events that happened prior to the transition into New Style dates. For example, the birthday of General and President George Washington is recognised (and historically was celebrated until 1970) as being 22 February 1732, even though the calendar in use at the time Washington was born read 11 February 1731 on the date of his birth.

Through enactment of the Calendar (New Style) Act 1750, Britain and the British Empire (including the eastern part of what is now the United States) adopted the Gregorian calendar in 1752, by which time it was necessary to correct by 11 days. Wednesday, 2 September 1752, was followed by Thursday, 14 September 1752. Claims that rioters demanded "Give us our eleven days" grew out of a misinterpretation of a painting by William Hogarth.[11] The British tax year traditionally began on Lady Day (25 March) on the Julian calendar and thus became 5 April, which was the "Old Style" equivalent.[12] A 12th skipped Julian leap day in 1800 changed its start to 6 April. It was not changed when a 13th Julian leap day was skipped in 1900, so the tax year in the United Kingdom still begins on 6 April.

The European colonies of the Americas adopted the change when their mother countries did. In Alaska, the change took place after the United States purchased Alaska from Russia. Friday, 6 October 1867 was followed by Friday, 18 October. Instead of 12 days, only 11 were skipped, and the day of the week was repeated on successive days, because at the same time the International Date Line was moved, from following Alaska's eastern border with Canada to following its new western border, now with Russia.[13]

Usually, the mapping of new dates onto old dates with a start of year adjustment works well with little confusion for events which happened before the introduction of the Gregorian calendar. For example, the Battle of Agincourt is universally known to have been fought on 25 October 1415, which is Saint Crispin's Day. But for the period between the first introduction of the Gregorian calendar on 15 October 1582 and its introduction in Britain on 14 September 1752, there can be considerable confusion between events in continental western Europe and in British domains. Events in continental western Europe are usually reported in English language histories as happening under the Gregorian calendar. For example, the Battle of Blenheim is always given as 13 August 1704. However confusion occurs when an event involves both. For example, William III of England arrived at Brixham in England on 5 November (Julian calendar), after setting sail from the Netherlands on 11 November (Gregorian calendar), in 1688.[14] For this reason, letters concerning diplomacy and international trade sometimes bore both old and new style dates to prevent confusion: for example, Sir William Boswell writing to Sir John Coke from The Hague dated a letter "12/22 Dec. 1635".[14]

The Battle of the Boyne in Ireland took place a few months later on 1 July 1690 "Old Style". This maps to 11 July new style, but because of the date of a subsequent battle it is commemorated as "The Twelfth" on 12 July "New Style" by a public holiday in Northern Ireland, with the Orange parades, and is an exception to the usual historical method of commemorating events of that period within Great Britain and Ireland by mapping the Julian date directly onto the modern Gregorian calendar (as happens for example with Guy Fawkes Night on 5 November).

Because of the differences, English people and their correspondents often employed two dates, dual dating, more or less automatically. In his biography of Dr John Dee, The Queen's Conjurer, Benjamin Woolley surmises that because Dee fought unsuccessfully for England to embrace the 1583/84 date set for the change, "England remained outside the Gregorian system for a further 170 years, communications during that period customarily carrying two dates, one 'O.S.' or Old Style, the other 'N.S.' or New Style."[15] In contrast, Thomas Jefferson, who lived during the time that the British Isles and colonies eventually converted to the Gregorian calendar, instructed that his tombstone bear his date of birth in the Old Style and his date of death in the New Style.[16] At Jefferson's birth the difference was eleven days between the Julian and Gregorian calendars; thus his birthday of 2 April in the Old Style is 13 April in the New Style. Similarly, George Washington is nowadays officially reported as having been born on 22 February 1732, rather than on 11 February 1731/32 O.S.[17] After the conversion to the Gregorian calendar, Washington celebrated his birthday according to the New Style calendar (as if he had been born on 22 February).[citation needed] Many British people, however, continued to celebrate their holidays "Old Style" well into the 19th century, a practice that according to the author Karen Bellenir reveals a deep emotional resistance to calendar reform.[18]

The need for change arose from the realisation that the correct figure for number of days in a year is not 365.25 (365 days 6 hours) as supposed by the Julian calendar but almost exactly 365.2425 days (365 days 5 hours 49 minutes 12 seconds), a reduction of 10 minutes 48 seconds per year: the Julian calendar has too many leap years. The consequence was that the basis for calculation of the date of Easter as decided in the fourth century had drifted from reality. The Gregorian calendar reform also dealt with the accumulated difference between these figures, between 325 and 1582 (1750 in the British Empire), by skipping 10 dates (11 in the case of the UK and her colonies) to restore the date of the vernal equinox to approximately March 21, the approximate date it occurred at the time of the First Council of Nicea in 325.

For a ready reckoner to assist in converting O.S. dates to N.S. and vice versa, see this table.

^British official legal documents of the 16th and 17th centuries were usually dated by the regnal year of the monarch. As these commence on the day and date of the monarch's accession, they normally span two consecutive calendar years and have to be calculated accordingly, but the resultant dates should be unambiguous.

^Stockton, J.R. Date Miscellany I: The Old and New Styles "The terms 'Old Style' and 'New Style' are now commonly used for both the 'Start of Year' and 'Leap Year' [(Gregorian calendar)] changes (England & Wales: both in 1752; Scotland: 1600, 1752). I believe that, properly and historically, the 'Styles' really refer only to the 'Start of Year' change (from March 25th to January 1); and that the 'Leap Year' change should be described as the change from Julian to Gregorian."

^ abcSpathaky, Mike Old Style and New Style Dates and the change to the Gregorian Calendar. "Before 1752, parish registers, in addition to a new year heading after 24th March showing, for example '1733', had another heading at the end of the following December indicating '1733/4'. This showed where the Historical Year 1734 started even though the Civil Year 1733 continued until 24th March. ... We as historians have no excuse for creating ambiguity and must keep to the notation described above in one of its forms. It is no good writing simply 20th January 1745, for a reader is left wondering whether we have used the Civil or the Historical Year. The date should either be written 20th January 1745 OS (if indeed it was Old Style) or as 20th January 1745/6. The hyphen (1745-6) is best avoided as it can be interpreted as indicating a period of time."

^Spathaky, Mike Old Style and New Style Dates and the change to the Gregorian Calendar. "An oblique stroke is by far the most usual indicator, but sometimes the alternative final figures of the year are written above and below a horizontal line, as in a fraction, thus: 173334{\displaystyle 17{\tfrac {33}{34}}}. Very occasionally a hyphen is used, as 1733-34."